Bottom water reservoir, often with a big water body and enough fluid supply, can supply its formation energy used in exploiting crude oil immediately by bottom water. The production rate will be seriously affected once water breakthrough in horizontal wells during the development process. Based on the numerical simulation, the relationship of horizontal section length, height of water avoidance, producing pressure drop and water breakthrough time, cumulative recovery of water-free period and water cut has been studied in this paper, and the reasonable dimensionless horizontal section length, dimensionless height of water avoidance and producing pressure drop are respectively 0.75, 0.9 and 1.0 MPa. The results show that the influence degree on water breakthrough from high to low is respectively producing pressure drop, dimensionless height of water avoidance and dimensionless horizontal section length; and the influence degree on cumulative recovery of water-free period from high to low is respectively height of water avoidance, horizontal section length and producing pressure drop. A big height of water avoidance and a small producing pressure drop and a long horizontal section length could prolong the water breakthrough time and increase the cumulative recovery of water-free period and is more beneficial to develop the bottom water reservoir.%底水油藏往往表现为水体能量大,流体补给充足,开采原油所消耗的地层能量可由底水及时补充,在其开发过程中,水平井一旦见水,将严重影响产量.以油藏数值模拟为手段,研究了水平段长度、无因次水平段避水高度、生产压差与见水时间、无水期累积采油量及含水率的关系,并优化出合理的水平段长度、无因次水平段避水高度和生产压差,其值分别为375m,0.9和1.0 MPa.应用正交设计试验极差分析法,研究了水平段长度、无因次水平段避水高度和生产压差对水淹规律的综合影响,结果表明,水平井参数对见水时间的影响程度由大到小依次为:生产压差、无因次水平段避水高度、水平段长度；对无水期累积采油量的影响程度由大到小依次为:无因次水平段避水高度、水平段长度、生产压差；较大的无因次水平段避水高度、较小的生产压差和较长的水平段长度可以延长水平井的见水时间,提高无水期累积采油量,更有利于底水油藏水平井开发.
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